New 1,2-oxaphospholanes are prepared by the reaction of .alpha., .beta.-unsaturated ketones and dialkyl phosphites.
The reaction of dialkyl phosphites with .alpha., .beta.-unsaturated ketones has previously been thoroughly investigated by various experts. It has hitherto been considered the rule that in the reaction only 1 mole of phosphite is added to the double bond forming the .gamma.-ketophosphonates (see Houben-Weyl, Methoden der Organischen Chemie, vol. 12/1, pages 465-467, G. Thieme Verlag, Stuttgart, 1963). If diphosphonates were also obtained, these occured in moderate yield in addition to the monophosphonates (A. N. Pudovik, Zhurnal Obshch. Khim. 22, 1371, (1952), Chem. Abstr., 47, 4837, (1953). It was therefore surprising that in the process described herein 2 moles of phosphite are added easily. It was furthermore surprising that the .gamma.-phosphono-.alpha.-hydroxyphosphonates evidently formed as intermediate cyclize under the reaction conditions rapidly and virtually completely to give the 1,2-oxaphospholane-5-phosphonates.
The reaction of 1 mole of acetylacetone, a .beta.-diketone, with 2 moles of diethyl phosphite was reported by B. A. Arbuzov et al, Izv. Akad. Nauk. SSSR, Ser Khim 12, 2757 (1971) to give 2-oxo-2-ethoxy-3-hydroxy-3,5-dimethyl-5-diethylphosphono-1,2-oxaphospholan e. This compound, although somewhat related to the compounds of this invention, possesses quite different chemical properties due to the 3-hydroxy group, and can undergo a variety of chemical reactions unavailable to the instant compounds.